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Gravity changes due to overpressure sources in 3D heterogeneous media: application to Campi Flegrei caldera, Italy
Language
English
Obiettivo Specifico
3.6. Fisica del vulcanismo
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
1/51 (2008)
Publisher
INGV
Pages (printed)
119-133
Issued date
February 2008
Last version
http://hdl.handle.net/2122/2715
Abstract
Employing a 3D finite element method, we develop an algorithm to calculate gravity changes due to pressurized
sources of any shape in elastic and inelastic heterogeneous media. We consider different source models, such as
sphere, spheroid and sill, dilating in elastic media (homogeneous and heterogeneous) and in elasto-plastic media.
The models are oriented to reproduce the gravity changes and the surface deformation observed at Campi
Flegrei caldera (Italy), during the 1982-1984 unrest episode. The source shape and the characteristics of the
medium have great influence on the calculated gravity changes, leading to very different values for the source
densities. Indeed, the gravity residual strongly depends upon the shape of the source. Non negligible contributions
also come from density and rigidity heterogeneities within the medium. Furthermore, if the caldera is elasto-
plastic, the resulting gravity changes exhibit a pattern similar to that provided by a low effective rigidity. Even
if the variation of the source volumes is quite similar for most of the models considered, the density inferred for
the source ranges from ∼400 kg/m3 (super critical water) to ∼3300 kg/m3 (higher than trachytic basalts), with
drastically different implications for risk assessment.
sources of any shape in elastic and inelastic heterogeneous media. We consider different source models, such as
sphere, spheroid and sill, dilating in elastic media (homogeneous and heterogeneous) and in elasto-plastic media.
The models are oriented to reproduce the gravity changes and the surface deformation observed at Campi
Flegrei caldera (Italy), during the 1982-1984 unrest episode. The source shape and the characteristics of the
medium have great influence on the calculated gravity changes, leading to very different values for the source
densities. Indeed, the gravity residual strongly depends upon the shape of the source. Non negligible contributions
also come from density and rigidity heterogeneities within the medium. Furthermore, if the caldera is elasto-
plastic, the resulting gravity changes exhibit a pattern similar to that provided by a low effective rigidity. Even
if the variation of the source volumes is quite similar for most of the models considered, the density inferred for
the source ranges from ∼400 kg/m3 (super critical water) to ∼3300 kg/m3 (higher than trachytic basalts), with
drastically different implications for risk assessment.
References
BATTAGLIA, M., and P. SEGALL (2004): The interpretation of
gravity changes and crustal deformation in active volcanic
areas, Pure Appl. Geophys., doi: 10.1007/
s00024-004-2514-5.
BATTAGLIA, M., C. TROISE, F. OBRIZZO, F. PINGUE and G. De
NATALE (2006): Evidence for fluid migration as the
source of deformation at Campi Flegrei caldera (Italy),
Geophys. Res. Lett., doi: 10.1029/2005GL024904.
BERRINO, G. (1994): Gravity changes induced by heightmass
variations at Campi Flegrei caldera, J. Volcanol.
Geotherm. Res., 61, 293-309.
BERRINO, G., G. CORRADO, G. LUONGO and B. TORO (1984):
Ground deformation and gravity change accompanying
the 1984 Pozzuoli uplift, Bull. Volcanol., 47, 187-200.
BONAFEDE, M. and M. MAZZANTI (1998): Modelling gravity
variations consistent with ground deformation in the
Campi Flegrei caldera (Italy), J. Volcanol. Geotherm.
Res., 81, 137-157.
BROCHER, T.M. (2005): Empirical relations between elastic
wavespeeds and density in the earth’s crust, Bull.
Seism. Soc. Am., 95, 2081-2092.
BULLETTIN VOLCANOLOGIQUE (1984): The 1982-1984
bradyseismic crisis at Campi Flegrei, Italy, Bull. Volcanol.,
47.
CHIODINI, G., M. TODESCO, S. CALIRO, C. DEL GAUDIO, G.
MACEDONIO and M. RUSSO (2003): Magma degassing
as a trigger of bradyseismic event: the case of Phlegrean
Fields (Italy), Geophys. Res. Lett., 30, doi: 10.1029/
2002GL016790.
CURRENTI, G., C. DEL NEGRO and G. GANCI (2007): Modelling
of ground deformation and gravity fields using finite
element method: an application to Etna volcano,
Geophys. J. Int., 169, 775-786, doi: 10.1111/j.1365-
246X.2007.03380.x.
DE NATALE, G., F. PINGUE, P. ALLARD and A. ZOLLO (1991):
Geophysical and geochemical modelling of the 1982-
1984 unrest phenomena at Campi Flegrei caldera (Southern
Italy), J. Volcanol. Geotherm. Res., 48, 199-222.
DIETERICH, J.H. and R.W. DECKER (1975): Finite element
modelling of surface deformation associated with volcanism,
J. Geophys. Res., 80, 4094-4102.
FERNANDEZ, J. and J.B. RUNDLE (1994): Gravity changes and
deformation due to a magmatic intrusion in a two layered
crustal model, J. Geophys. Res., 99, 2737-2746.
FERNANDEZ, J., K.F. TIAMPO and J.B. RUNDLE (2001): Viscoelastic
displacement and gravity changes due to
point magmatic intrusions in a gravitational layered
solid Earth, Geophys. J. Int., 146, 155-170.
FRANCHINI, L. (2005): Deformazioni e variazioni della
gravità in aree vulcaniche: influenza della struttura reologica,
in italian, Università degli Studi di Bologna,
Corso di Laurea Specialistica in Fisica.
GOTTSMANN, J., H. RYMER and G. BERRINO (2006): Unrest
at the Campi Flegrei caldera (Italy): a critical evaluation
of source parameters from geodetic data inversion,
J. Volcanol. Geotherm. Res., 150, 132-145.
GREENBERG, M.D. (1978): Foundations of Applied Mathematics
(Prentice-Hall, Inc., Englewood Cliffs, New Jersey),
pp. 456.
MARC (1994): Analysis Research Corporation (Palo Alto,
CA).
SASAI, Y. (1986): Multiple tension-crack model for dilatancy:
surface displacement, gravity and magnetic change,
Bull. Earth. Res. Inst., 61, 429-473.
TRASATTI, E., C. GIUNCHI and M. BONAFEDE (2005): Structural
and rheological constraints on source depth and
overpressure estimates at the Campi Flegrei caldera,
Italy, J. Volcanol. Geotherm. Res., 144, 105-118.
TRASATTI, E., C. GIUNCHI and N.P. AGOSTINETTI (2008): Numerical
inversion of deformation caused by pressure
sources: application to Mt. Etna (Italy), Geophys. J. Int.,
172, 873-884, doi: 10.111/j.1365-246x.2007.03677.x.
WALSH, J.B. and J.R. RICE (1979): Local changes in gravity
resulting from deformation, J. Geophys. Res., 84,
165-170.
WANG, R.F., F.L. MARTÌN and F. ROTH (2006), PSGRN/
PSCMP a new code for calculating co- and post-seismic
deformation, geoid and gravity changes based on
the viscoelastic-gravitational dislocation theory, Comput.
Geosci., 32, 527-541.
YANG, X., P.M. DAVIS and J.H. DIETERICH (1988): Deformation
from inflation of a dipping finite prolate spheroid
in an elastic halfspace as a model for volcanic stressing,
J. Geophys. Res., 93, 4249-4257.
gravity changes and crustal deformation in active volcanic
areas, Pure Appl. Geophys., doi: 10.1007/
s00024-004-2514-5.
BATTAGLIA, M., C. TROISE, F. OBRIZZO, F. PINGUE and G. De
NATALE (2006): Evidence for fluid migration as the
source of deformation at Campi Flegrei caldera (Italy),
Geophys. Res. Lett., doi: 10.1029/2005GL024904.
BERRINO, G. (1994): Gravity changes induced by heightmass
variations at Campi Flegrei caldera, J. Volcanol.
Geotherm. Res., 61, 293-309.
BERRINO, G., G. CORRADO, G. LUONGO and B. TORO (1984):
Ground deformation and gravity change accompanying
the 1984 Pozzuoli uplift, Bull. Volcanol., 47, 187-200.
BONAFEDE, M. and M. MAZZANTI (1998): Modelling gravity
variations consistent with ground deformation in the
Campi Flegrei caldera (Italy), J. Volcanol. Geotherm.
Res., 81, 137-157.
BROCHER, T.M. (2005): Empirical relations between elastic
wavespeeds and density in the earth’s crust, Bull.
Seism. Soc. Am., 95, 2081-2092.
BULLETTIN VOLCANOLOGIQUE (1984): The 1982-1984
bradyseismic crisis at Campi Flegrei, Italy, Bull. Volcanol.,
47.
CHIODINI, G., M. TODESCO, S. CALIRO, C. DEL GAUDIO, G.
MACEDONIO and M. RUSSO (2003): Magma degassing
as a trigger of bradyseismic event: the case of Phlegrean
Fields (Italy), Geophys. Res. Lett., 30, doi: 10.1029/
2002GL016790.
CURRENTI, G., C. DEL NEGRO and G. GANCI (2007): Modelling
of ground deformation and gravity fields using finite
element method: an application to Etna volcano,
Geophys. J. Int., 169, 775-786, doi: 10.1111/j.1365-
246X.2007.03380.x.
DE NATALE, G., F. PINGUE, P. ALLARD and A. ZOLLO (1991):
Geophysical and geochemical modelling of the 1982-
1984 unrest phenomena at Campi Flegrei caldera (Southern
Italy), J. Volcanol. Geotherm. Res., 48, 199-222.
DIETERICH, J.H. and R.W. DECKER (1975): Finite element
modelling of surface deformation associated with volcanism,
J. Geophys. Res., 80, 4094-4102.
FERNANDEZ, J. and J.B. RUNDLE (1994): Gravity changes and
deformation due to a magmatic intrusion in a two layered
crustal model, J. Geophys. Res., 99, 2737-2746.
FERNANDEZ, J., K.F. TIAMPO and J.B. RUNDLE (2001): Viscoelastic
displacement and gravity changes due to
point magmatic intrusions in a gravitational layered
solid Earth, Geophys. J. Int., 146, 155-170.
FRANCHINI, L. (2005): Deformazioni e variazioni della
gravità in aree vulcaniche: influenza della struttura reologica,
in italian, Università degli Studi di Bologna,
Corso di Laurea Specialistica in Fisica.
GOTTSMANN, J., H. RYMER and G. BERRINO (2006): Unrest
at the Campi Flegrei caldera (Italy): a critical evaluation
of source parameters from geodetic data inversion,
J. Volcanol. Geotherm. Res., 150, 132-145.
GREENBERG, M.D. (1978): Foundations of Applied Mathematics
(Prentice-Hall, Inc., Englewood Cliffs, New Jersey),
pp. 456.
MARC (1994): Analysis Research Corporation (Palo Alto,
CA).
SASAI, Y. (1986): Multiple tension-crack model for dilatancy:
surface displacement, gravity and magnetic change,
Bull. Earth. Res. Inst., 61, 429-473.
TRASATTI, E., C. GIUNCHI and M. BONAFEDE (2005): Structural
and rheological constraints on source depth and
overpressure estimates at the Campi Flegrei caldera,
Italy, J. Volcanol. Geotherm. Res., 144, 105-118.
TRASATTI, E., C. GIUNCHI and N.P. AGOSTINETTI (2008): Numerical
inversion of deformation caused by pressure
sources: application to Mt. Etna (Italy), Geophys. J. Int.,
172, 873-884, doi: 10.111/j.1365-246x.2007.03677.x.
WALSH, J.B. and J.R. RICE (1979): Local changes in gravity
resulting from deformation, J. Geophys. Res., 84,
165-170.
WANG, R.F., F.L. MARTÌN and F. ROTH (2006), PSGRN/
PSCMP a new code for calculating co- and post-seismic
deformation, geoid and gravity changes based on
the viscoelastic-gravitational dislocation theory, Comput.
Geosci., 32, 527-541.
YANG, X., P.M. DAVIS and J.H. DIETERICH (1988): Deformation
from inflation of a dipping finite prolate spheroid
in an elastic halfspace as a model for volcanic stressing,
J. Geophys. Res., 93, 4249-4257.
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